My 99 Bravada keeps blowing the fuse. I have pretty much pulled entire harness out of the loom, unplugged ICM, coil, Crank Position sensor, Injectors and still blows fuse. Is there anything on this circuit that I should eliminate? Also, according to the wiring diagram I have, this should only be hot when the key is in the start or run position. Why would I have voltage at the terminal(s) where the fuse plugs in with the key off? I'm at my wits end with this. Most recent repair was replacing the fuel pump, which shouldn't matter because it's not on the same circuit, correct?

 

OK, update. The terminals are not hot on both sides, i'm an idiot. I did find out that what seems to be a short is in whatever wire feeds the hot side of the fuse. I unplugged the middle section from underneath the fuse box which is all the components that the ecm feeds and still blew the fuse. Does anyone know what color wire that is, and is it from the ignition? I have the wiring diagram from Autozone website, but that doesn't tell me what wire or color feeds this.

 

The HOT side of the ECM 1 fuse is fed by either a bus bar or a wire. The ECM 1 fused side most likely feeds a bus bar with 10 pink wires connected to it. The 10 circuits exit the fuse panel via:
Connector C2,
Pins:
B10, (2 wires) = feeds ignition control module & ignition coil
C10, (2 wires) = feeds injectors 2 & 6
D10, (2 wires) = feeds injectors 3 & 5
E10, (2 wires) = feeds injectors 1 & 3
F10, (1 wire) = feeds crankshaft position sensor

Connector C1 pin B10, (1 wire) feeds the PCM.


If it's blowing the fuse with all this stuff disconnected, the components are obviously not the problem and each wire will need to be traced to locate the short to ground. The easiest way would be to check resistance from each of the pins mentioned above in the fuse panel connectors, to ground. Each of the components must be disconnected from its harness, including connectors C1 & C2 at the fuse panel. Should show infinite resistance indicating an open circuit.

 

All wires seem good, did get resistance on F9 (two pink wires). What do these wires feed? or if it's possible, can you post the diagram? Also when plugging back in C1 connector I heard something come on, kinda sounded like the starter might have been trying to engage. Any thoughts/ideas on that?

 

The ignition switch feeds ECM 1 fuse through a pink wire in C1 pin A9, not a buss bar as I mentioned earlier. It should show battery voltage in the START & RUN positions.

There are 61 pages to look through, might take a while to find F9

 

OK, I figured out the noise was the transfer case motor coming on. Anyone have any explanation why the transfer case motor would come on? BTW, still can't figure out where the short is that is causing the ECM fuse to blow. Would a bad ECM cause this?

 

Disconnecting and re connecting the battery re-boots the TCCM. It's normal for it to momentarily command the encoder motor when it boots up.

It's possible the ECM is shorted, but very unlikely. These PCM's are darn near bulletproof and rarely fail. I'd continue checking the wiring, bound to be a short to ground somewhere.